verilogams $rdist_normal for random resistor value in a transient simulation

I'm trying to generate a Gaussian random resistor value for each transient simulation with the following verilogams code:

`include "constants.vams"
`include "disciplines.vams"

module Rrandom (va, vb);

inout va, vb;
electrical va, vb;
parameter real Rmean = 200.0*63.0;
parameter real Rstdev = 100;
parameter integer seed = 23;

real Rval;

analog
begin
  Rval = $rdist_normal( seed, Rmean, Rstdev, "instance" );
  I(va, vb) <+ V(va,vb)/Rval;
end

endmodule

When I run in "Single Run, Sweeps and Corners" mode the Rval is changing on every timepoint.  Here is a plot of the Rval for one of the resistors in the netlist:

But I'd like to have a single value for the resistor throughout the simulation (not changing per timepoint).  I tried moving the $rdist_normal outside the analog block as a "parameter real" similar to the example shown in the "Cadence Verilog-A Language Reference 21.1" in the $arandom section (but using $rdist_normal) but that gives me a syntax error.

`include "constants.vams"
`include "disciplines.vams"

module Rrandom (va, vb);

inout va, vb;
electrical va, vb;
parameter real Rmean = 200.0*63.0;
parameter real Rstdev = 100;
parameter integer seed = 23;

parameter real Rval = $rdist_normal( seed, Rmean, Rstdev, "instance" );

analog
begin
  I(va, vb) <+ V(va,vb)/Rval;
end

endmodule

How can I get resistor with a Gaussian distribution that does not change every simulation timepoint in the transient run?